16 Library introduction [library]

16.5 Library-wide requirements [requirements]

16.5.4 Constraints on programs [constraints]

16.5.4.11 Requires paragraph [res.on.required]

Violation of any preconditions specified in a function's Requires: element results in undefined behavior unless the function's Throws: element specifies throwing an exception when the precondition is violated.
Violation of any preconditions specified in a function's Preconditions: element results in undefined behavior.